Conventionally, a pressure detector includes a first member having a sensing portion, a second member having a diaphragm for receiving pressure and a pressure transmission member. The sensing portion detects the pressure and outputs an electric signal corresponding to the applied pressure. The diaphragm receives the applied pressure. The pressure transmission member transmits the pressure received by the diaphragm to the sensing portion.
In the conventional detector, the sensing portion, the pressure transmission member and the diaphragm are provided by different parts. These three parts contact together so as to sandwich the pressure transmission member between the sensing portion and the diaphragm. Thus, excess load is applied to these three parts.
In the detector, the pressure received by the diaphragm is transmitted to the sensing portion through the pressure transmission member. The sensing portion outputs the electric signal in accordance with the applied and transmitted pressure. Thus, the detector detects the pressure.
This detector is manufactured as follows.
The pressure transmission member is inserted between the sensing portion and the diaphragm. Then, a preliminary load is applied to the sensing portion through the diaphragm and the pressure transmission member.
In this case, the preliminary load is applied to the diaphragm with load application equipment through a jig. Thus, the diaphragm is pressed by a predetermined amount. Under this condition, the first member and the second member are welded. Thus, the pressure detector is manufactured.
However, in a conventional method for manufacturing the pressure detector, the preliminary load is determined on the basis of a measurement value obtained by mechanically measuring the load applied with load application equipment through the jig. This determination step of the preliminary load mechanically measured is a step of measuring a pressing force through the jig. Therefore, the measured preliminary load may have measurement error, compared with the actual preliminary load. This error may be caused by tolerance of parts, tolerance of assembly or deviation of contact condition of the pressure transmission member. Thus, there is a possibility to cause big deviation between the measured preliminary load and the actual preliminary load.
This deviation causes measurement error of the pressure detector, since the preliminary load to the detection element and the pressure receiving diaphragm are deviated largely.